International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

In the Republic of Kosovo, the unemployment rate has an increasing trend, the average monthly income is still low, which makes it impossible to buy a new vehicle, so they are forced to buy vehicles imported from European countries, which have a h igh rate of amortization.
Citizens who own used vehicles are obliged to perform services that cost less by avoiding quality equipment and replacing them with non-know manufactures for spare parts which cost cheaper compared to manufacturers of well-known and guaranteed brands. The use of such spare parts is directly affecting the increase in the number of accidents in the territory of the Republic of Kosovo. In this paper is study the efficiency of brake pads from different manufacturers – brands in the term of the braking system in passenger vehicles such as: braking time, maximum deceleration and braking distance. The tests were done with used vehicles equipped with the ABS system, on roads with dry asphalt. The used tires are from radial construction with summer characteristics. Depending on the treated methodology, the adequate equipment such as Xl meter, video cameras and meter are used. The obtained results through the decelerometer device (Xl meter) for deceleration of the vehicle and other indicators of the efficiency of the braking system has done with the case of emergency braking. Prior to each test, the predicted used vehicle has performed also technical inspection of the vehicle braking system in the Licensed Centers for technical inspection of the vehicle.

The article is devoted to the analysis of the most used additives for lubricants. The principle of their operation and the result of their work are considered. The effect of additives on the structure of surface layers on the surface of friction pairs is est imated. The analysis showed the use of only a limited number of principles of the action of antifriction additives. Theoretically promising antifriction additives for base oils, relevant for use in railway transport, have been proposed.

The paper considers the impact of functionalized nanosized carbon particles on the physicomechanical characteristics of composite materials based on polyamides. The concentration of the modifier varied both in the field of “doping” concentrations and in the field of concentrations used in the industrial production of nanocomposite materials based on polymer matrices. It was found that the use of cryogenic treatment of the initial polyamide leads to an increase in physical and mechanical characteristics. The introduction of nanodispersed particles in the field of “doping” concentrations increases the strength and hardness of the developed compositions based on a polyamide matrix.

The agricultural industry is growing very quickly. Large areas of fields make tractors work at higher speeds, with which they also move on public roads. Except acceleration, the agricultural tractor must also be stopped. There are emergency situations on the roads that require sudden braking, and therefore a quick stop of the vehicle. Drum brakes are used in most farm tractors. They contain a friction pair (shoes and drum) which as a result of cooperation changes the kinetic energy of the motion into thermal energy. Unfortunately, this crates huge amount of this energy. This can cause overheating of the friction lining, which can lead to permanent damage. This paper presents the results of simulation tests of the heating process during single emergency braking. It has been shown that in some situations the temperature can reach a higher value than that which is safe for friction material components.

One of the main problems in the plastic deformation of materials is the determination of the coefficient of friction as well as the subsequent application of the simulation for comparative analysis. However forecasting process and matching between simulation and experimental data is still a problem. Causes of this are factors such as roughness, mechanical properties of the material, chemical composition, etc. which strongly influence the behavior of the material in the simulation of the process.

In this study, an approach is proposed to determine the changeable coefficient of friction in the deformation process experimentally, taking into account implicitly the influence of surface roughness on the friction curves. For the comparative analysis between experiment and simulation of the process, the experimental data for objective assessment was introduced. Nevertheless, there are differences between experiment and simulation, which is most evident in high loads, using lubricants differing from more than 12 units for graphite lubricant, with more than 6 units with oil and with dry friction with 8 units.

The structure and physicomechanical characteristics of vacuum coatings formed from refractory metal compounds on steel substrates of different chemical composition are studied. The possibility of applying refractory metal coatings to protect metal substrates used for the manufacture of metalworking tools and steel tools used for casting non-ferrous metals has been analyzed.

In the present work, the adhesion and physico-mechanical characteristics of heat-resistant vacuum coatings formed on steel substrates are investigated. An increase in the values of adhesion and physico-mechanical parameters of coatings formed from multicomponent compounds is established. The tribotechnical characteristics of coatings based on chromium carbonitride have been studied.

The article deals with forming the adhesive bond of bodies at the crystal lattice level. There is offered a mathematical model for determining the adhesion wear. There are carried out laboratory tests for model validation. There is found that the amount of adhesive wear is nonline-arly dependent on the surface roughness inclination angle.

The effect of metal phase composition in the Fe-based + (2 % glass) powdered composites on the basic mechanical and tribological properties of the composites, made by means of sintering and hot forging, have been investigated. As a basis for the metallic phase of the composite the mixtures of iron powders with additives of graphite, B₄C, BN and Cu at different ratio were used. It was shown that at sintering of metal-glass material the reaction of glass phase with oxides on the surface of iron powder particles takes place, resulting in a change of glass phase chemical composition. The results of materials mechanical properties investigations had shown that the highest strength properties and hardness have the composites with the content of the initial powder mixture of 5% Cu and 2% B₄C, while the best tribological properties have the composites with 2% B₄C, 5% Cu and 1% BN.

Wear, is one of the most important failure type which reduces the service lifetime and increases the maintenance cost of machines. In addition, wear is directly related with surface properties and friction characteristics. So, researchers focus on various surface treatments to reduce the wear and its cost. Plasma nitriding is one of surface treatment which forms a few hundred micron diffusion zone and a surface inter-metallic phases with moderate surface hardness. PVD coating is another method which ensures ultra-hard and a few micron surface layers. In the present study, AISI H13 hot work tool steel substrate was surface treated with various methods, such as plasma nitriding, PVD coating and duplex treatment. Effects of the treatments on the surface roughness, hardness were investigated. Additionally, microstructural analysis was performed to present the effect of treatments on the surface microstructures. Furthermore, friction characteristics were investigated using ball on disk testing machine and wear tracks were discussed using optical microscopy.

In this paper was investigated the formation of complex diffusion boride layers on metastable austenite Cr-Mn-N steel powder method. Calculate the value of the diffusion coefficient in different physical – chemical conditions and the thermodynamic potential chemical reactions. Defined phase composition layers obtained on the metastable austenite Cr-Mn-N steel. It is established that the application of an external magnetic field (EMF) leads to a redistribution of the proportion boride phases in the surface layers, changes the period of crystal lattice and increasing the diffusion coefficient.

In this paper we study the structure, phase composition, microhardness, crack resistance, wear resistance boride coatings obtained at complex saturation with boron and copper in the application of an external magnetic field (EMF). Investigations have shown that this method allows the application of boride coatings in 1.5 – 2 times decrease the duration saturation detail, and receive coating with high hardness, wear resistance, crack resistance.

It is established that the application EMF formed a continuous, homogeneous boride layer with thickness coatings in 2 times higher than boride coatings without EMF for the equal duration of the process. When imposing EMF in boride layers observed the redistribution quantitative relation boride phases, namely: decrease of volume phase FeB, and on diffractograms surface layers boride coatings obtained after boriding fixed presence phases FeB and Fe₂B. After complex saturation boron and copper in the application of external magnetic fields fixed phases FeB and Cu.

The researches have shown that the highest spalling stress value is reached in boride phases, obtained in powder environments with copper powder at the application of EMF, and respectively is 420 compared with 225 MPa for coating obtained without EMF. Increased shear stress values in complex layers obtained after saturation with boron and copper caused by the formation of phases more viscosity, for which crack K_1c in 1.4 – 2.0 times higher than the initial boride phases FeB and Fe₂B.

Application of EMF at boriding improves tribological characteristics of coatings: decreases coefficient of friction and increase in 1.5 – 2.5 times wear resistance.